1. Field of the Invention
The present invention relates to a structure for mounting an object on a mounting base, in which vibration of the object is suppressed.
2. Description of Related Art
A structure for mounting an object on a mounting structure with a resilient member disposed therebetween to suppress vibration of the object has been known hitherto. For example, JP-U-64-55380 and JP-U-7-41160 disclose a structure for mounting an electromagnetic valve for controlling an amount of purge gas on an intake manifold of an automotive engine. A rubber grommet is supported on a stay connected to the electromagnetic valve, and a bolt is inserted into a hole of the grommet and a tip of the bolt is screwed into the intake manifold. In this manner, the electromagnetic valve is resiliently mounted on the intake manifold to thereby suppress vibration of the electromagnetic valve.
In the conventional mounting structure, a metallic sleeve is disposed in a hole of the grommet into which a threaded portion of the bolt is inserted. The metallic sleeve is used to prevent direct contact between the hole of the grommet and the threaded portion of the bolt while allowing the grommet to be properly compressed. In the conventional structure, however, the number of parts constituting the mounting structure increases by using the metallic sleeve. Further, a thickness of the grommet in the radial direction has to be reduced due to presence of the metallic sleeve because a mounting space on the intake manifold is limited. The thinner grommet reduces effectiveness of the grommet in suppressing vibration.
On the other hand, when the electromagnetic valve is heavy or its axial length is long, it is highly possible that the electromagnetic valve may be slanted by vibration force. If the grommet for resiliently mounting the electromagnetic valve is positioned close to the intake manifold on which the electromagnetic valve is mounted, a valve port of the electromagnetic valve contacts an inside wall of the mounting hole, and operating noises of the valve will be propagated to the intake manifold.
In the mounting structures shown in JP-U-64-55380 and JP-U-7-41160 mentioned above, it is proposed to place a supporting position (a position where a bolt is screwed into the mounting base) as closer as possible to a gravity center of the electromagnetic valve. However, this makes a shape of the intake manifold complex. To cope with this problem, it may be conceived to place the supporting position apart from the mounting base by using a longer bolt and to eliminate a metallic sleeve disposed in the grommet hole. In this structure, however, a rod portion of the bolt, where a thread is not formed, directly contacts an inner wall of the grommet hole, and the grommet is deformed by abrasion force generated when the bolt is screwed into the intake manifold. If the grommet is too much deformed, the grommet will be damaged by cracks or the like, and its durability will be decreased. If an amount of compression of the grommet is reduced to avoid cracks, the electromagnetic valve may not be correctly held on the intake manifold.